1. Field of the Invention
This invention relates to a control system of logical units present in a disk storage apparatus, and to a computer system comprising the disk storage apparatus and one or a plurality of host computers.
2. Description of the Related Art
A computer system, in which one or a plurality of disk storage apparatuses having a plurality of logical units are connected to a plurality of host computers through high-speed interfaces such as a Fibre Channel and these host computers share one or a plurality of disk storage apparatuses, is known. However, there is a strong demand in such a computer system for storing information inherent to each host computer, such as an OS, in the disk storage apparatus having a high-speed interface, such as a Fibre Channel, and shared by a plurality of host computers, rather than in a disk storage apparatus having an ATA (Advanced Technology Attachment) or SCSI (Small Computer System Interface) interface and connected discretely to each host computer, from the aspects of high-speed performance and cost. In order to store the information inherent to each host computer in the disk storage apparatus shared by a plurality of host computers, it is essentially necessary to control exclusively the logical unit, that stores the information inherent to each host computer, as the logical unit dedicated to the individual host computer.
When a plurality of host computers and one or a plurality of disk storage apparatuses are connected by the Fibre Channel, the physical interface is generally the Fibre Channel and the logical interface is generally the SCSI.
In the SCSI, a Reserve/Release command and a Persistent Reserve In/Out command are stipulated as the commands for exclusively managing the logical units. However, to manage exclusively the logical unit dedicated to each host computer for other host computers in these SCSI commands, the following problems are yet to be solved.
In the Reserve/Release command, the Reserve condition of the logical unit is released if the power source of the disk storage apparatus is cut off or the disk storage apparatus is reset. Therefore, the logical unit dedicated to each host computer cannot be managed exclusively at the time of making of the power source.
In the Persistent Reserve In/Out command, the Persistent Reserve condition is not released even when the power source of the disk storage apparatus is cut off or the disk storage apparatus is reset. However, because other host computer holding a Reservation Key can change the Persistent Reserve condition, the logical unit dedicated to each host computer cannot completely be managed exclusively.
To manage exclusively the logical unit dedicated to each host computer, a mechanism becomes necessary that exclusively manages the logical unit inside the disk storage apparatus without relying on exclusive management by the SCSI command.
Conventional control systems of the logical units of the disk storage apparatuses are described in xe2x80x9cSCSI Bus Systemxe2x80x9d (JP-A-6-44181) and xe2x80x9cConversion Method of Block Address and Control Method of Rotary Type Storage Sub-Systemxe2x80x9d (JP-A-9-62452), for example. When this control system is constituted by the conventional disk storage apparatus, there is no other means at present than the method using Reserve/Release command or the Persistent Reserve In/Out command of the SCSI in order to exclusively manage the logical units. Therefore, it has not been possible to completely manage exclusively the logical unit dedicated to each host computer.
On the other hand, in the conventional disk storage apparatuses and host computers, the logical disk number that is assigned for managing the logical disk inside the disk storage apparatus is coincident with the logical disk number assigned for managing the logical disk inside the host computer. If the host computer designates the same logical unit number, therefore, access is made to the same logical unit inside the disk storage apparatus when all the host computers gain access to this logical unit.
When the host computer and the disk storage apparatus are connected mutually through the interface, the host computer designates serially the logical unit numbers from 0 to each disk storage apparatus at the time of making of the power source, sends the Inquiry command of the SCSI and recognizes the disk storage apparatus and the logical unit inside the disk storage apparatus. Generally, the host computer keeps sending the Inquiry command serially from the logical unit number 0 until it detects from the response of the Inquiry command that the logical unit in the designated disk storage apparatus does not exist. Therefore, the serial numbers are allotted to the logical units inside the host computer, and the logical units are so managed.
In such a computer system, there is a strong demand for storing a shared application and data, that are used in the computer system, in the disk storage apparatus that has a high-speed interface such as the Fibre Channel and is shared by a plurality of host computers, from the aspects of maintenance and the cost. Generally, the conventional disk storage apparatuses incorporate the logical unit having the number 0.
In a computer system in which a plurality of host computers share one or a plurality of disk storage apparatuses, an object of the present invention is that it proposes an internal mechanism of a disk storage apparatus that exclusively manages its logical units for the host computers without using an SCSI command for exclusive management.
The disk storage apparatus includes a hard disk drive and a disk array. The hard disk drive comprises a disk control portion and a disk drive. The disk control portion comprises a host interface control portion, a host management portion, a logical unit management portion, an address conversion portion, a command processing portion, a drive cache, a drive cache control portion, a drive control portion and a data bus.
The disk array has a mechanism that achieves high performance and high reliability of the disk system. To attain high-speed performance, a physical hard disk drive is allowed to function apparently as one hard disk drive for the host computer in the disk array. To attain high reliability, on the other hand, redundant data for data recovery is stored in other hard disk drive if any trouble occurs in the hard disk drive that stores the data.
The disk array comprises one or a plurality of disk array controllers and a plurality of hard disk drives. Fibre Channel, SCSI, and so forth are used as the interface between the disk array controller and a plurality of hard disk drives. Each disk array controller comprises a host interface control portion, a host management portion, a logical unit management portion, an address conversion portion, a command processing portion, a drive interface control portion, a drive cache and a drive cache control portion.
In order to achieve the object of the present invention, in a computer system in which a plurality of host computers and one or a plurality of disk storage apparatuses having a plurality of logical units are connected to one another by the Fibre Channel as the physical interface and by SCSI as the logical interface in FC-AL (Fibre Channel Arbitrated Loop) topology, a disk storage apparatus according to the present invention includes a logical unit correspondence memory portion for storing the correspondence between the logical unit number allotted by and in the host computer and the logical unit number allotted by and in the disk storage apparatus, and a logical unit number conversion portion for converting the logical unit number designated by the corresponding host computer through the SCSI command by using the logical unit correspondence memory portion to the logical unit number in the disk storage apparatus, both portions being provided to the logical unit management portion of the disk storage apparatus. The logical unit management memory portion includes a logical unit correspondence setting portion for setting the correspondence between the logical unit number allotted by and in the host computer and the logical unit number allotted by and in the disk storage apparatus.
The function of the disk control portion of the hard disk drive and its operation will be explained. The host interface control portion controls the FC-AL signals and the protocol, and executes the Link control with the host computers, the address management on the loop of the hard disk drive, the SCSI command reception, the data flow control, and the response transmission to the SCSI command. The host management portion stores and manages the communication environment information inherent between the Fibre Channel Ports of the host computer and the disk storage apparatus using Word Wide Names (WWN) that is the inherent address to the Fibre Channel port of the host computer.
The logical unit management portion manages the physical position and the capacity of each logical unit of the hard disk drive. It also manages exclusively the logical units for the host computers. To execute this exclusive management, the logical unit number conversion means converts the logical unit number designated by the SCSI command to the logical unit number inside the hard disk drive.
The address conversion portion converts the logical block address (LBA) designated by the SCSI command to the physical position of the disk drive.
The data bus is an internal bus for executing the data transfer between the host interface and the disk drive.
The command processing unit interprets the SCSI command received from the host computer and controls its execution.
The drive cache is a temporary memory for absorbing the difference of the data transfer rate between the host interface and the disk drive, and is managed by the cache management portion.
The drive control portion manages the format of the disk drive and controls data write/read to and from the disk drive.
Next, the function of the disk array controller and its operation will be explained. The portions other than the address conversion portion and the drive interface portion have the same functions as those of the corresponding disk control portion of the hard disk drive. The explanation will be given hereby on the address conversion portion and the drive interface control portion.
The address conversion portion converts the request of the SCSI command transmitted by the host computer to the SCSI command for the hard disk drive inside the disk array.
The drive interface control portion controls the interface between the disk array controller and the hard disk drive inside the disk array, transmits the command, that is converted and generated by the address conversion portion, to the hard disk drive, and controls thus the data flow between the disk array controller and the hard disk drive.
The logical unit number correspondence setting means, that is provided afresh in the present invention, associates on the 1:1 basis the number, that is allotted inside the disk storage apparatus to the logical unit dedicated to each host computer, with the logical unit number allotted inside the corresponding host computer, and sets the correspondence relation to the logical unit correspondence memory means. On the other hand, this correspondence setting means associates the number allotted inside the disk storage apparatus to the logical unit, shared by a plurality of host computers, with the logical unit numbers allotted by and in a plurality of host computers, and sets this correspondence relation to the logical unit correspondence memory means.
The logical unit number conversion means converts the logical unit number, that is designated by the host computer for each command by using the WWN inherent to each Fibre Channel Port of the host computer and the logical unit correspondence memory means to the logical unit number allotted inside the disk storage apparatus. Therefore, the logical unit management portion using the logical unit number conversion means can manage exclusively the logical unit, that is useful for each host computer, for other host computers. When the logical unit correspondence memory means, the logical unit correspondence setting means and the logical unit number conversion means according to the present invention are employed, the logical unit storing the information inherent to each host computer can be managed exclusively without using the SCSI command for exclusive management.